The Guillotine

If the laws are such that a person must die for the crimes he or she has committed, surely the most instantaneous and therefore the most merciful method is death by means of the guillotine. Execution by hanging is always open to doubt, the timespan between initial strangulation and final oblivion is not known. The sword and the axe allow too much leeway for the victim to flinch or the executioner to mis-aim. And even the multi-executioners of a firing squad cannot guarantee that at least one bullet will penetrate the heart. Most other methods are similarly flawed, whether they be by gas poisoning, electric chair or whatever. [Lethal drugs don't always get the job done properly either.] In other words, there is nothing so instantly final as a head severed by a machine.

Geoffrey Abbott, Lords of the Scaffold, 2001